US4987601A - Acoustic apparatus - Google Patents

Acoustic apparatus Download PDF

Info

Publication number
US4987601A
US4987601A US07/389,737 US38973789A US4987601A US 4987601 A US4987601 A US 4987601A US 38973789 A US38973789 A US 38973789A US 4987601 A US4987601 A US 4987601A
Authority
US
United States
Prior art keywords
port
opening portion
air
resonator
shape
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US07/389,737
Other languages
English (en)
Inventor
Motoomi Goto
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Yamaha Corp
Original Assignee
Yamaha Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Yamaha Corp filed Critical Yamaha Corp
Assigned to YAMAHA CORPORATION, A CORP. OF JAPAN reassignment YAMAHA CORPORATION, A CORP. OF JAPAN ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: GOTO, MOTOOMI
Application granted granted Critical
Publication of US4987601A publication Critical patent/US4987601A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R1/00—Details of transducers, loudspeakers or microphones
    • H04R1/20—Arrangements for obtaining desired frequency or directional characteristics
    • H04R1/22—Arrangements for obtaining desired frequency or directional characteristics for obtaining desired frequency characteristic only 
    • H04R1/28—Transducer mountings or enclosures modified by provision of mechanical or acoustic impedances, e.g. resonator, damping means
    • H04R1/2807—Enclosures comprising vibrating or resonating arrangements
    • H04R1/2815—Enclosures comprising vibrating or resonating arrangements of the bass reflex type
    • H04R1/2823—Vents, i.e. ports, e.g. shape thereof or tuning thereof with damping material
    • H04R1/2826—Vents, i.e. ports, e.g. shape thereof or tuning thereof with damping material for loudspeaker transducers
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H04R3/002—Damping circuit arrangements for transducers, e.g. motional feedback circuits

Definitions

  • the present invention relates to an acoustic apparatus in which a vibrator is disposed in a Helmholtz resonator having an open duct port and a cavity.
  • FIGS. 5A and 5B are respectively a perspective view and a sectional view showing an arrangement of a bass-reflex speaker system.
  • a hole is formed in the front surface of a cabinet 1, and a vibrator (dynamic speaker unit) 4 constituted by a diaphragm 2 and a transducer 3 is mounted in this hole.
  • An open duct port 6 having a sound path 5 open to an external portion is arranged below the vibrator 4.
  • a resonance frequency f op defined by an air spring in the cabinet 1 and an air mass in the sound path 5 is set to be lower than a lowest resonance frequency f oc of the vibrator when it is assembled in a bass-reflex type cabinet.
  • the phase of a sound pressure from the rear surface of the diaphragm 2 is inverted at the sound path 5, and hence, a sound directly radiated from the front surface of the diaphragm 2 is in-phase with a sound from the sound path 5, thus increasing the sound pressure.
  • the frequency characteristic of the output sound pressure can be expanded below the resonance frequency f oc of the vibrator.
  • a uniform reproduction range can be extended as compared to that of an infinite plane baffle or a closed baffle.
  • FIG. 7 shows an arrangement of an acoustic apparatus (speaker system with a resonance port) shown the U.S. patent application No. 07/286,869 which was assigned to the same assignee as the present application.
  • the resonance frequency f op of a Helmholtz resonator is set to be lower than that of the bass-reflex speaker system shown in FIGS. 5A and 5B.
  • a vibrator for driving the Helmholtz resonator is driven to cancel an air counteraction from the resonator when the resonator is driven.
  • the acoustic apparatus can be made compact and can reproduce a lower bass sound.
  • an opening portion of the open duct port is extended in a horn-like shape, so that the open duct port communicates with a port mounting surface with a smooth curvature, and an air-flow diffusing body corresponding to the shape of the port opening portion is provided at the center of the extended port opening portion.
  • the present inventor closely examined an air communication state of an open duct port in a conventional bass-reflex speaker system or a speaker system with a resonance port according to the application U.S.S. No. 286,869, which comprises a Helmholtz resonator in which a sound path of the open duct port constituting the Helmholtz resonator is open to an external portion with a constant sectional area.
  • U.S.S. No. 286,869 which comprises a Helmholtz resonator in which a sound path of the open duct port constituting the Helmholtz resonator is open to an external portion with a constant sectional area.
  • equivalent elements L, C, and R of a resonance system have directivity. Namely, the equivalent elements L, C, and R in the air inlet mode are different from those in the air outlet mode, thus causing a distortion in a resonant acoustic wave.
  • an opening portion of the open duct port is extended in a horn-like shape (like a flower of a morning glory), so that the open duct port communicates with a port mounting surface with a smooth curvature, and an air-flow diffusing body corresponding to the shape of the port opening portion is provided at the center of the extended port opening portion.
  • the air inlet path is rendered smooth, and the shape of the flow path is improved so that an outlet air flow passes along the same path as an inlet air flow. In this manner, air outlet and inlet modes for the open duct port can be equalized.
  • the difference in the resonance system between the air outlet and air inlet modes as a cause of the distortion of a resonant acoustic wave can be eliminated or prevented, and as a result, the distortion of the resonant acoustic wave can be eliminated.
  • FIG. 1 is a schematic view for explaining an arrangement of an acoustic apparatus according to an embodiment of the present invention
  • FIG. 2 is a graph showing a frequency characteristic of a sound pressure of an acoustic wave radiated from the acoustic apparatus shown in FIG. 1;
  • FIGS. 3A and 3B are equivalent circuit diagrams of a resonance system in the acoustic apparatus shown in FIG. 1;
  • FIG. 4A is an enlarged sectional view of an air-duct opening portion of the acoustic apparatus shown in FIG. 1;
  • FIG. 4B is a perspective view showing a mounting state of an air diffusing device shown in FIG. 4A;
  • FIGS. 5A and 5B are respectively a perspective view and a sectional view showing an arrangement of a conventional bass-reflex speaker system
  • FIG. 6 is a graph for explaining a sound pressure characteristic of the speaker system shown in FIG. 7;
  • FIG. 7 is a schematic view for explaining an arrangement of a speaker system with a resonance port according to the application U.S.S. No. 286,869.
  • FIG. 1 shows an arrangement of an acoustic apparatus according to an embodiment of the present invention.
  • the shape of an air duct (open duct port) 6 of the speaker system with the resonance port shown in FIG. 7 is improved.
  • FIG. 7 a hole is formed in the front surface of a cabinet 1, and a dynamic speaker unit (vibrator) 4 constituted by a diaphragm 2 and a transducer 3 is mounted in this hole.
  • An air duct (open duct port) 6 having a sound path 5 open to the outside of the cabinet 1 is arranged below the speaker unit 4.
  • the air duct 6 and the cabinet 1 form a Helmholtz resonator. In this Helmholtz resonator, an air resonance phenomenon occurs by an air spring in the cabinet 1 as a closed cavity and an air mass in the sound path 5 of the air duct 6.
  • the resonance frequency f op of this resonator is given by: ##EQU1## where c is the sonic speed, S is the sectional area of the sound path 5, ⁇ is the length of the air duct 6, and V is the volume of the cabinet 1.
  • a vibrator driver 30 for driving the speaker unit 4 comprises a servo section 31 for performing electrical servo to cancel an air counteraction from the resonator side when the Helmholtz resonator constituted by the cabinet 1 and the air duct 6 is driven.
  • a servo system can adopt a negative impedance generator for equivalently generating a negative impedance component (-Z 0 ) in an output impedance, a motional feedback (MFB) circuit for detecting a motional signal corresponding to a movement of the diaphragm 2 by a certain means and feeding back the detected signal to an input side, or the like.
  • the transducer 3 when a drive signal is supplied from the vibrator driver 30 to the transducer 3 of the speaker unit 4, the transducer 3 electro-mechanically converts the drive signal to reciprocate the diaphragm 2 in the back-and-forth direction (right-and-left direction in FIG. 1).
  • the diaphragm 2 mechano-acoustically converts this reciprocal motion.
  • the front surface side (right surface side in FIG. 1) of the diaphragm 2 serves as a direct radiation portion for directly externally radiating an acoustic wave, and the rear surface side (left surface side in FIG.
  • the diaphragm 2 serves as a resonator driving portion for driving the Helmholtz resonator constituted by the cabinet 1 and the air duct 6.
  • An air counteraction from air in the cabinet 1 is applied to the rear surface side of the diaphragm 2.
  • the vibrator driver 30 drives the speaker unit 4 to cancel this air counteraction.
  • the diaphragm 2 cannot be driven from the resonator side, and serves as a rigid body, i.e., a wall viewed from the resonator side.
  • the resonance frequency and Q value of the Helmholtz resonator are independent from those of the direct radiation portion defined by the diaphragm 2 of the speaker unit 4.
  • a resonator driving energy from the speaker unit 4 is applied independently of the direct radiation portion.
  • the speaker unit 4 Since the speaker unit 4 is driven in a so-called "dead" state wherein it is not influenced by the air counteraction from the resonator, i.e., the cabinet 1 side, the frequency characteristic of the direct radiation portion is not influenced by the volume of the cabinet 1. Therefore, with this arrangement, the volume of the cabinet 1 as the cavity of the Helmholtz resonator can be reduced to be smaller than that of the conventional bass-reflex speaker system. In this case, if the resonance frequency f op is set to be lower than that of this bass-reflex speaker system, a sufficient Q value can be assured. As a result, in the acoustic apparatus of this embodiment, when the cabinet 1 is reduced in size to be smaller than that of the conventional bass-reflex speaker system, a lower bass sound can be reproduced.
  • the speaker unit 4 drives the diaphragm 2 in response to the drive signal from the vibrator driver 30, and independently supplies a drive energy to the Helmholtz resonator constituted by the cabinet 1 and the air duct 6.
  • an acoustic wave is directly radiated from the direct radiation portion (diaphragm 2), as indicated by an arrow a in FIG. 1, and air in the cabinet 1 is resonated, so that an acoustic wave at a sufficient sound pressure is resonantly radiated from a resonant radiation portion (the opening 7 of the air duct 6).
  • a frequency characteristic of the sound pressure as shown in, e.g., FIG.
  • a curve a represents a frequency characteristic of a sound pressure of an acoustic wave directly radiated from the diaphragm 2
  • a curve b represents a frequency characteristic of a sound pressure of an acoustic wave resonantly radiated from the opening 7.
  • the air duct 6 is elongated as compared to the conventional bass-reflex speaker system. Since the diaphragm 2 of the speaker unit 4 is strongly driven to cancel an air counteraction from the resonator side, the flow rate of an air flow communicating through the air duct 6 is very high. In addition, when the air duct 6 is open to an external portion while it has a uniform sectional area, as shown in FIG. 7, the air flows such that the air flows out from the central portion of the air duct 6 and flows in from the inner edge portion of the air duct 6.
  • the effective sectional areas for the air flow are different in the outlet and inlet modes, and equivalent elements L, C, and R of the resonance system have different values in the outlet (FIG. 3A) and inlet (FIG. 3B) modes, as shown in the equivalent circuits of FIGS. 3A and 3B.
  • a resonant acoustic wave is distorted.
  • the shape of an opening portion 6a of the air duct 6 is improved to equalize air flow outlet and inlet paths.
  • the cylindrical air duct (open duct port) 6 having a sectional area S o is extended at its opening portion (port opening portion) 6a in a horn-like shape (like a flower of a morning glory) to communicate with an air duct mounting surface (baffle surface) 1a of the cabinet 1 with a smooth curvature.
  • An air diffusing device 8 having a shape according to the curvature of the air duct opening portion 6a is supported by a support member 9 at the center of the opening 7, as shown in FIG. 4B.
  • curvature formation of the horn-like shape of the air duct opening portion 6a can be relatively easily realized using, e.g., a resin molded cabinet.
  • the shape of the air duct 6 of the speaker system with the resonance port is improved such that the opening portion 6a extending from the opening side edge portion of the uniform shape portion 6b of the air duct 6 to the baffle mounting portion has a smooth curvature, and the air diffusing device 8 is attached at the central portion of the opening 7 of the air duct 6 so that the effective area S 2 -S 1 of the air flow path defined by the air duct opening portion 6a and the air diffusing device 8 is equalized to the air duct area S o .
  • the outlet air flow from the center of the air duct is guided along the diffusing device 8 having a smooth curvature, and passes the same path as the inlet air flow.
  • the effective sectional areas for the outlet and inlet air flows of the duct 6 are equalized, thus eliminating a distortion of a resonant acoustic wave.
  • the present invention is applied to the speaker system with the resonance port shown in FIG. 7.
  • the present invention is applicable to various other acoustic apparatuses such as a conventional bass-reflex speaker system, in which a vibrator is disposed in a Helmholtz resonator having an open duct port and a cavity.
  • the present invention is applied to the opening portion 6a of the open duct port to the outside of the cabinet.
  • the present invention may be applied to an opening portion 6c (FIG. 1) to the interior of the cabinet or to both the opening portions 6a and 6c.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Health & Medical Sciences (AREA)
  • Otolaryngology (AREA)
  • Details Of Audible-Bandwidth Transducers (AREA)
  • Obtaining Desirable Characteristics In Audible-Bandwidth Transducers (AREA)
US07/389,737 1988-08-10 1989-08-04 Acoustic apparatus Expired - Lifetime US4987601A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP1988104947U JPH0727750Y2 (ja) 1988-08-10 1988-08-10 音響装置
JP63-104947[U] 1988-08-10

Publications (1)

Publication Number Publication Date
US4987601A true US4987601A (en) 1991-01-22

Family

ID=14394289

Family Applications (1)

Application Number Title Priority Date Filing Date
US07/389,737 Expired - Lifetime US4987601A (en) 1988-08-10 1989-08-04 Acoustic apparatus

Country Status (2)

Country Link
US (1) US4987601A (de)
JP (1) JPH0727750Y2 (de)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5073945A (en) * 1989-07-24 1991-12-17 Matsushita Electric Industrial Co., Ltd. Loudspeaker system
EP0530575A1 (de) * 1991-09-04 1993-03-10 Pioneer Electronic Corporation Flare speaker
US5261006A (en) * 1989-11-16 1993-11-09 U.S. Philips Corporation Loudspeaker system comprising a helmholtz resonator coupled to an acoustic tube
WO1996006514A1 (en) * 1994-08-23 1996-02-29 Polk Investment Corporation Ported loudspeaker system and method with reduced air turbulence
US5675131A (en) * 1993-12-16 1997-10-07 Kabushiki Kaisha Toshiba Speaker system and the same for television sets
US5892183A (en) * 1997-07-26 1999-04-06 U.S. Philips Corporation Loudspeaker system having a bass-reflex port
DE102004021546A1 (de) * 2004-05-03 2005-12-08 Avantgarde Acoustic Lautsprechersysteme Gmbh Hornlautsprecher
US20060052992A1 (en) * 2004-08-16 2006-03-09 Allan Devantier Method for predicting loudspeaker port performance and optimizing loudspeaker port designs utilizing bi-directional fluid flow principles
US20080226088A1 (en) * 2005-09-20 2008-09-18 Koninklijke Philips Electronics, N.V. Audio Transducer System
US7711134B2 (en) * 2001-06-25 2010-05-04 Harman International Industries, Incorporated Speaker port system for reducing boundary layer separation
US8064627B2 (en) 2007-10-22 2011-11-22 David Maeshiba Acoustic system
WO2013010017A1 (en) * 2011-07-12 2013-01-17 Strata Audio LLC Balanced momentum inertial duct
GB2577569A (en) * 2018-09-29 2020-04-01 Barefaced Ltd Loudspeaker enclosure with slot/horn apparatus for improved polar response and low frequency output

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH0226890Y2 (de) * 1985-07-03 1990-07-20

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4135600A (en) * 1976-01-19 1979-01-23 Trio Kabushiki Kaisha Loudspeaker system
US4213515A (en) * 1977-09-15 1980-07-22 Novanex Automation N.V. Speaker system
US4276443A (en) * 1979-08-17 1981-06-30 Meyers Stanley T Sound reproducing system utilizing motional feedback and velocity-frequency equalization

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4135600A (en) * 1976-01-19 1979-01-23 Trio Kabushiki Kaisha Loudspeaker system
US4213515A (en) * 1977-09-15 1980-07-22 Novanex Automation N.V. Speaker system
US4276443A (en) * 1979-08-17 1981-06-30 Meyers Stanley T Sound reproducing system utilizing motional feedback and velocity-frequency equalization

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5073945A (en) * 1989-07-24 1991-12-17 Matsushita Electric Industrial Co., Ltd. Loudspeaker system
US5261006A (en) * 1989-11-16 1993-11-09 U.S. Philips Corporation Loudspeaker system comprising a helmholtz resonator coupled to an acoustic tube
EP0530575A1 (de) * 1991-09-04 1993-03-10 Pioneer Electronic Corporation Flare speaker
US5675131A (en) * 1993-12-16 1997-10-07 Kabushiki Kaisha Toshiba Speaker system and the same for television sets
US5517573A (en) * 1994-01-04 1996-05-14 Polk Investment Corporation Ported loudspeaker system and method with reduced air turbulence
WO1996006514A1 (en) * 1994-08-23 1996-02-29 Polk Investment Corporation Ported loudspeaker system and method with reduced air turbulence
EP1515585A2 (de) * 1994-08-23 2005-03-16 Britannia Investment Corporation Bassreflexlautsprechersystem und -verfahren mit reduzierter Luftturbulenz
EP1515585A3 (de) * 1994-08-23 2005-06-22 Britannia Investment Corporation Bassreflexlautsprechersystem und -Verfahren mit reduzierter Luftturbulenz
US5892183A (en) * 1997-07-26 1999-04-06 U.S. Philips Corporation Loudspeaker system having a bass-reflex port
US7711134B2 (en) * 2001-06-25 2010-05-04 Harman International Industries, Incorporated Speaker port system for reducing boundary layer separation
DE102004021546A1 (de) * 2004-05-03 2005-12-08 Avantgarde Acoustic Lautsprechersysteme Gmbh Hornlautsprecher
US20060052992A1 (en) * 2004-08-16 2006-03-09 Allan Devantier Method for predicting loudspeaker port performance and optimizing loudspeaker port designs utilizing bi-directional fluid flow principles
US7890312B2 (en) 2004-08-16 2011-02-15 Harman International Industries, Incorporated Method for predicting loudspeaker port performance and optimizing loudspeaker port designs utilizing bi-directional fluid flow principles
US20080226088A1 (en) * 2005-09-20 2008-09-18 Koninklijke Philips Electronics, N.V. Audio Transducer System
US8064627B2 (en) 2007-10-22 2011-11-22 David Maeshiba Acoustic system
US20120061174A1 (en) * 2007-10-22 2012-03-15 David Maeshiba Acoustic system
WO2013010017A1 (en) * 2011-07-12 2013-01-17 Strata Audio LLC Balanced momentum inertial duct
US8744108B2 (en) 2011-07-12 2014-06-03 Strata Audio LLC Balanced momentum inertial duct
GB2577569A (en) * 2018-09-29 2020-04-01 Barefaced Ltd Loudspeaker enclosure with slot/horn apparatus for improved polar response and low frequency output
GB2577569B (en) * 2018-09-29 2022-06-15 Barefaced Ltd Loudspeaker enclosure with slot/horn apparatus for improved polar response and low frequency output

Also Published As

Publication number Publication date
JPH0226890U (de) 1990-02-21
JPH0727750Y2 (ja) 1995-06-21

Similar Documents

Publication Publication Date Title
US5004066A (en) Acoustic apparatus
US5173575A (en) Acoustic apparatus
US5012890A (en) Acoustic apparatus
US4987601A (en) Acoustic apparatus
US5313525A (en) Acoustic apparatus with secondary quarterwave resonator
US5109422A (en) Acoustic apparatus
US4943956A (en) Driving apparatus
US5261006A (en) Loudspeaker system comprising a helmholtz resonator coupled to an acoustic tube
EP0336303A2 (de) Akustischer Apparat
US5009281A (en) Acoustic apparatus
US4164988A (en) Fine tuned, column speaker system
US5150417A (en) Bass reflex type speaker system
US4997057A (en) Method and apparatus of expanding acoustic reproduction range
US5031500A (en) Keyboard instrument
US4987564A (en) Acoustic apparatus
WO2001037611A1 (en) System and method to enhance reproduction of sub-bass frequencies
JP2003517805A (ja) ２つの外部通気孔及び１つの内部通気孔が設けられる２重チャンバ音響エンクロージャを有するスピーカ
US4410064A (en) Bass response speaker housing and method of tuning same
US5248846A (en) Musical instrument incorporating a Helmholtz resonator
US4989187A (en) Acoustic apparatus
US5009280A (en) Acoustic apparatus
US5898788A (en) Loudspeaker system
US4027115A (en) Electroacoustic sound generator
GB2037534A (en) Loudspeakers
JPH0229794A (ja) 携帯用楽器

Legal Events

Date Code Title Description
AS Assignment

Owner name: YAMAHA CORPORATION, 10-1, NAKAZAWA-CHO, HAMAMATSU-

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:GOTO, MOTOOMI;REEL/FRAME:005111/0131

Effective date: 19890722

STCF Information on status: patent grant

Free format text: PATENTED CASE

FPAY Fee payment

Year of fee payment: 4

FEPP Fee payment procedure

Free format text: PAYOR NUMBER ASSIGNED (ORIGINAL EVENT CODE: ASPN); ENTITY STATUS OF PATENT OWNER: LARGE ENTITY

FPAY Fee payment

Year of fee payment: 8

FPAY Fee payment

Year of fee payment: 12